1. Field
Embodiments of the present invention relate to a disc brake, and more particularly, to a disc brake capable of stably returning a piston after a braking operation is terminated while improving the effect of return of a piston.
2. Description of the Related Art
A disc brake is an apparatus for braking a vehicle by forcedly causing friction pads to be pressed against both sides of a disc that rotates together with a wheel of the vehicle to stop the disc rotating. In the disc brake, a parking brake configured to keep a vehicle stationary is used at the time of parking.
In general, a disc brake includes one pair of pad plates disposed at both sides of a disc that rotates with a wheel of a vehicle and compress the disc to generate a braking force, a carrier supporting the pad plates, a caliper housing slidably installed on the carrier to compress the pad plates and equipped with a piston moved by hydraulic braking pressure, and an actuator configured to operate the piston in a mechanical manner.
The actuator is connected to a parking cable for operating the actuator, and the parking cable is manually or automatically operated by being connected to a parking cable manipulating apparatus that is operated by a parking lever directly manipulated by a driveror an electro motive apparatus.
There are two types of actuating. One is a cam-strut actuating that uses a cam rotated by operation of a parking cable and a strut installed between the cam and a piston. The other is a ball-in-ramp actuating that includes a fixed ramp plate fixedly installed in a caliber housing, a rotating ramp plate rotated by operation of a parking cable, a ball installed between the fixed ramp plate and the rotating ramp plate to advance the rotating ramp plate at the time of rotation of the rotating ramp plate, a push rod provided adjacent to the rotating ramp plate to push a piston, and a spring returning the push rod to the original position thereof.
In general, the ball-in-ramp scheme is referred to as a BIR (ball-in-ram) caliper type, and BIR caliper type disc brake is disclosed in Korean Patent Publication No. 10-2011-0029267. According to the disclosure, a rotating ramp plate pushes a push rod by rotating and advancing, and the push rod pushes a piston such that disc pads come into close contact with a disc.
The BIR caliper type disc brake does not have a subsidiary member securing a predetermined running clearance between a disc and pad plates in the initial braking, which causes friction pads installed on the pad plate to unnecessarily make friction with the disc, leading to abrasion of the friction pads and noise resulting therefrom. In addition, a short restoring distance at the time of releasing the brake leads to a drag in which the friction pads are not sufficiently separated from the disc and thus the friction pads are worn out.